In-Situ Anode Activation By A Cathode In An Alkaline Water Electrolytic Cell

ABSTRACT

An electrolytic cell for alkaline water electrolysis with in-situ anode activation comprising: an anode; a cathode wherein at least a part of a surface of the cathode comprises an electrically conducting stable material and an anode catalytic material adapted to be released from the surface of the cathode in alkaline water and be deposited at a surface of the anode when an electric voltage is applied across the anode and the cathode; and a diaphragm separating the anode and the cathode, wherein the diaphragm is gas tight and is permeable to the anode catalytic material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Application of InternationalApplication No. PCT/EP2016/057047 filed Mar. 31, 2016, the contents ofwhich are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to electrolysis. Various embodiments mayinclude cells for alkaline water electrolysis with in-situ anodeactivation.

BACKGROUND

In modern times, electrolysis is used for various purposes, for examplein Hydrogen and/or Oxygen generation which are achieved by hydrogenevolution reaction (HER) and Oxygen evolution reaction (OER) duringelectrolysis of alkaline water used as an electrolyte in an electrolyticcell also referred to as an electrolyser. The electrolytic cell includeselectrodes, i.e. at least an anode and at least a cathode, that conductelectrical energy to the electrolyte and thus decomposes the electrolytein the electrolytic cell.

Various types of electrodes are used in the electrolytic cell, forexample, commonly used electrodes in the electrolytic cell are a Nickelcathode and a Nickel anode. The efficiency of alkaline waterelectrolysis is dependent on overpotential of the electrolytic cell andis increased by reducing the overpotential of the electrolytic cell,hereinafter also referred to as cell overpotential. The celloverpotential is significantly constituted by overpotential of theelectrodes i.e. the overpotential of the anode, hereinafter alsoreferred to as the anodic overpotential, and the overpotential of thecathode, hereinafter also referred to as the cathodic overpotential.

The anodic and the cathodic overpotentials are optimized, generallyreduced, by various approaches for example either by geometry changes inthe electrodes or by applying an electrocatalytic coating formingsurfaces of the electrodes. It is well known in the art of alkalinewater electrolysis that coating with different catalysts reduce theover-potential of the electrode that is coated and hence energyconsumption for the OER and the HER. For example, anodes are typicallycoated with various oxides of transition elements while cathodes aretypically composed of an underlying substrate such as stainless steel onwhich Raney nickel, nickel sulfide, etc. are coated. The variousapproaches to reduce the anodic and/or the cathodic overpotentials bysurface modification of the anode and/or the cathode are generallyreferred to as activation. It is customary to use an activated cathodeas well as an activated anode in the electrolytic cells for alkalinewater electrolysis to achieve an optimum efficiency of the electrolysis.

Activation of the anode and the cathode may be carried out separatelybefore the electrodes are installed in the electrolyser and before thealkaline water electrolysis is performed. Moreover, if and when any ofthe electrodes are to be replaced then the replacement electrodes arealso activated before the electrodes are installed in the electrolyserand restarting the electrolysis process in the electrolyser. Variousmethods are used to form an activated anode in addition to formation ofan activated cathode, and this requirement of activating the anodebefore being placed in the electrolytic cell increases at least cost andtime of production of the activated anode.

SUMMARY

The teachings of the present disclosure may be embodied in a techniquefor in-situ anode activation that can be performed in the electrolyticcell along with the electrolysis of the alkaline water.

For example, some embodiments may include an electrolytic cell (1) foralkaline water electrolysis with in-situ anode activation, theelectrolytic cell (1) comprising: an anode (10), a cathode (20) whereinat least a part of a surface of the cathode (20) comprises anelectrically conducting stable material (22) and an anode catalyticmaterial (21), the anode catalytic material (21) adapted to be releasedfrom the cathode (20) in alkaline water and be deposited at a surface ofthe anode (10) when an electric voltage is applied across the anode (10)and the cathode (20), and a diaphragm (30) disposed between the anode(10) and the cathode (20) wherein the anode (10) and the cathode (20)are separated by the diaphragm (30) and wherein the diaphragm (30) isgas tight and is permeable to the anode catalytic material (21).

In some embodiments, the electrically conducting stable material (22)comprises Nickel.

In some embodiments, the anode catalytic material (21) is one of Cobalt,Manganese, Molybdenum, Chromium, and a combination thereof.

In some embodiments, the anode catalytic material (21) in the cathode(20) is between 4 percentage by mass of the cathode (20) and 30percentage by mass of the cathode (20), and particularly between 10percentage by mass of the cathode (20) and 15 percentage by mass of thecathode (20).

In some embodiments, the part of the surface of the cathode (20) furthercomprises Sulfur.

In some embodiments, the anode (10) is made of only Nickel.

As another example, some embodiments may include a method (100) forin-situ anode activation of an anode (10) positioned in an electrolyticcell (1) for alkaline water electrolysis, the method (100) comprising: astep (110) of providing a cathode (20) wherein at least a part of asurface of the cathode (20) comprises an electrically conducting stablematerial (22) and an anode catalytic material (21), the anode catalyticmaterial (21) adapted to be released from the cathode (20) in alkalinewater, a step (120) of releasing the anode catalytic material (21) fromthe cathode (20) wherein a part of the anode catalytic material (21)from the cathode (20) is released from the cathode (20) into anelectrolyte (40) in the electrolytic cell (1) by positioning the cathode(20) in the electrolytic cell (1) such the surface of the cathode (20)is contacted with the electrolyte (40), wherein the electrolyte (40) isalkaline water and wherein the cathode (20) is positioned such that inthe electrolytic cell (1) the cathode (20) and the anode (10) areseparated by a diaphragm (30) configured to be gas tight and permeableto the anode catalytic material (21), and a step (140) of depositing theanode catalytic material (21) so released wherein at least a part of theanode catalytic material (21) so released is deposited at a surface ofthe anode (10) by applying an electric voltage across the anode (10) andthe cathode (20) such that an overpotential at the anode (10) is reducedby deposition of the anode catalytic material (21) at the surface of theanode (10).

In some embodiments, the step (120) of releasing the anode catalyticmaterial (21) from the cathode (20) into the electrolyte (40) isperformed at an open circuit potential of the electrolytic cell (1).

In some embodiments, there is a step (130) of sustained release of theanode catalytic material (21) from the cathode (20) subsequent to thestep (120) of releasing the anode catalytic material (21) from thecathode (20), wherein in the step (130) of sustained release of theanode catalytic material (21) at least a part of the anode catalyticmaterial (21) from the cathode (20) is released from the cathode (20)into the electrolyte (40) along with applying the external electricvoltage across the anode (10) and the cathode (20).

In some embodiments, the external electric voltage applied across theacross the anode (10) and the cathode (20) is corresponding to a pH ofthe electrolyte (40) and a molality of the anode catalytic material (21)present in the electrolyte (40).

In some embodiments, the electrically conducting stable material (22)comprises Nickel.

In some embodiments, the anode catalytic material (21) is one of Cobalt,Manganese, Molybdenum, Chromium, and a combination thereof.

In some embodiments, the anode catalytic material (21) in the cathode(20) is between 4 percentage by mass of the cathode (20) and 30percentage by mass of the cathode (20), and particularly between 10percentage by mass of the cathode (20) and 15 percentage by mass of thecathode (20).

In some embodiments, the part of the surface of the cathode (20) furthercomprises Sulfur.

In some embodiments, the anode (10) is made of only Nickel.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present disclosure are further describedhereinafter with reference to illustrated embodiments shown in theaccompanying drawing, in which:

FIG. 1 schematically illustrates an exemplary embodiment of anelectrolytic cell having a cathode with an anode catalytic materialincorporating teachings of the present disclosure;

FIG. 2 schematically illustrates an exemplary embodiment of theelectrolytic cell in a state subsequent to a state depicted in FIG. 1 ofthe electrolytic cell;

FIG. 3 schematically illustrates an exemplary embodiment of theelectrolytic cell in a state subsequent to a state depicted in FIG. 2 ofthe electrolytic cell;

FIG. 4 depicts a flow chart showing an exemplary embodiment of a methodincorporating teachings of the present disclosure; and

FIG. 5 graphically represents a relation between voltage applied, pH andrelease of the anode catalytic material from the cathode, incorporatingteachings of the present disclosure.

DETAILED DESCRIPTION

In some embodiments, an electrolytic cell for alkaline waterelectrolysis, hereinafter also referred to as the cell, includes a pairof electrodes having an anode and a cathode and a diaphragm.

The electrolytic cell may be an individual cell or a part of anelectrolyser stack. The diaphragm is disposed between the anode and thecathode and the anode and the cathode are separated by the diaphragm.The diaphragm is gas tight. The anode may be, but not limited to, formedof Nickel only.

At least a part of a surface of the cathode includes an electricallyconducting stable material, for example Nickel, and an anode catalyticmaterial, for example Cobalt, Molybdenum, Manganese, Chromium or acombination thereof. incorporating teachings of the present disclosurethe anode catalytic material in the cathode may be between 4 percentageby mass of the cathode and 30 percentage by mass of the cathode, andparticularly between 10 percentage by mass of the cathode and 15percentage by mass of the cathode. The anode catalytic material isadapted to be released from the cathode in alkaline water, when presentin the cell. The anode catalytic material may be released at opencircuit potential of the cell and/or may be released when an externalvoltage is applied to the cell. The electrically conducting stablematerial is stable in the cathode and is not released in the electrolyteor is released in insignificant amount over long period of usage typicalof electrolytic cells for alkaline water electrolysis.

In some embodiments, the diaphragm is permeable to anode catalyticmaterial and allows passage of anode catalytic material, especially inionic forms dissolved in or carried in the electrolyte into which theanode catalytic material gets released from the cathode, to pass throughit, i.e. the diaphragm, from cathode side of the electrolyte to theanode side of the electrolyte. The anode catalytic material may bedeposited at a surface of the anode when an electric voltage is appliedacross the anode and the cathode.

As a result of deposition of the anode catalytic material overpotentialof the anode is decreased and the anode becomes active. Since the anodeis being activated while in seat within the electrolytic cell, and alsoduring the running of the alkaline water electrolysis by application ofthe external voltage, the activation of the anode is in-situ and occurssimultaneously with the electrolysis of the electrolyte. This at leastpartly obviates the requirement of ex-situ pre-electrolysis activationof the anode.

Furthermore, since the anode catalytic material is being released in theelectrolyte from the cathode and since not the entire mass of the anodecatalytic material present in the cathode at the start of theelectrolysis is released from the cathode simultaneously, a sustainedand continuous availability of the anode catalytic material in theelectrolyte and subsequently at the anode for deposition on surface ofthe anode is possible, unlike an alternate scenario in which a similarmaterial intended to be deposited on the anode is presented in theelectrolytic cell in the electrolyte directly and thus is available allat once for deposition at the anode and thus the availability of thesimilar material is not sustained and continuous. The anode may bemaintained in the activated state for a longer period of time due toreplenishment of any deposited anode catalytic material that the anodemight release during the electrolytic process. Moreover, in case thereis a requirement to remove an existent anode and insert a new anode intothe electrolytic cell, then activation of the new anode happensaccording to the described technique without needing to replenish theanode catalytic material in the electrolytic cell.

In some embodiments, since the anode catalytic material is leaving thesurface of the cathode when it is released in the electrolyte, thecathode surface become porous or increased in porosity, and thus theoverpotential at the cathode is also maintained or decreased due to theporosity increase in the cathode due to release of the anode catalyticmaterial from the cathode.

In some embodiments, the part of the surface of the cathode furtherincludes Sulfur, i.e. the cathode if formed of the electricallyconducting stable material, the anode catalytic material and Sulfur forexample the cathode is formed of Nickel, Cobalt and Sulfur. The sulfuror parts of the sulfur from the cathode during electrolysis in theelectrolytic cells, also called electrolyser, is slowly and continuouslyremoved from the cathode into the electrolyte in the electrolyserleaving thereby the electrically conducting stable material, for examplenickel. The release of sulfur from the cathode further facilitatesrelease of the anode catalytic material from the cathode.

Some embodiments include a method for activating an anode, for example aNickel anode, positioned in an electrolytic cell for alkaline waterelectrolysis. In some embodiments, the method includes a step ofproviding a cathode. The cathode provided in the method may beunderstood same as the cathode presented in according to the previousaspect of the present technique. Subsequently, in the method, a step ofreleasing the anode catalytic material from the cathode is performed.

In the step of releasing the anode catalytic material a part of theanode catalytic material from the cathode is released from the cathodeinto an electrolyte, e.g. alkaline water, in the electrolytic cell bypositioning the cathode in the electrolytic cell such the surface of thecathode is contacted with the electrolyte. The cathode is positionedsuch that in the electrolytic cell the cathode and the anode areseparated by a diaphragm. The diaphragm is gas tight and permeable tothe anode catalytic material. The anode catalytic material, for exampleCobalt, Manganese, Molybdenum, Chromium, and/or a combination thereof,may be released at open circuit potential of the cell and/or may bereleased when an external voltage is applied to the cell.

In some embodiments, a step of depositing the anode catalytic materialis performed in which at least a part of the anode catalytic material soreleased is deposited at a surface of the anode by applying an electricvoltage across the anode and the cathode. As a result of deposition ofthe anode catalytic material at the anode overpotential at the anode isreduced thereby resulting into in-situ activation of the anode.

In some embodiments, a method further includes a step of sustainedrelease of the anode catalytic material from the cathode. The step ofsustained release is subsequent to the step of releasing the anodecatalytic material from the cathode and may be simultaneously performedalong with the step of depositing the anode catalytic material. In thestep of sustained release of the anode catalytic material at least apart of the anode catalytic material from the cathode is released fromthe cathode into the electrolyte along with applying the externalelectric voltage across the anode and the cathode. The external electricvoltage applied across the electrodes i.e. the anode and the cathodecorresponds to a pH of the electrolyte and a molality of the anodecatalytic material present in the electrolyte as a result of the releasefrom the cathode. The anode and the cathode overpotentials, as well asthe molality of the anode catalytic material present in the electrolyte,corresponds to pH, and in turn the external electric voltage applied ischanged or adjusted depending on the pH of the electrolyte.

In the following description, for purpose of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of one or more embodiments. It may be noted that theillustrated embodiments are intended to explain, and not to limit thescope of the teachings herein. It may be evident that such embodimentsmay be practiced without these specific details.

The teachings herein may be employed to provide an in-situ activation ofthe anode and thus obviating ex-situ pre-electrolysis activation of theanode. In some embodiments, in an electrolytic cell for alkaline waterelectrolysis, a cathode is used that includes an anode catalyticmaterial e.g. a material which when deposited on the anode will activatethe anode. Furthermore, the anode catalytic material is such that itgets released, mostly in ionic forms, from the cathode into theelectrolyte within the electrolytic cell.

A part of the ions of the anode catalytic material present in theelectrolyte as a result of the release from the cathode, then migratetowards the anode within the electrolyte under the influence of anexternal voltage applied across electrodes, the voltage using which thealkaline water electrolysis is being carried out. The migrating ions ofthe anode catalytic material in the electrolyte pass through a diaphragmwhich is substantially impermeable to gas but permeable to ions inelectrolyte. The migrating ions of the anode catalytic material in theelectrolyte pass through the diaphragm from the cathode side of theelectrolyte to the anode side of the electrolyte, the cathode and theanode sides of the electrolyte created by the diaphragm positionedbetween and separating the anode from the cathode. Some of the ions ofthe anode catalytic material in the electrolyte that pass into the anodeside of the electrolyte then get deposited at the anode under theinfluence of the voltage applied across the electrodes of theelectrolytic cell. The deposition of the anode catalytic materialreduces the anodic overpotential and thus results into activation of theanode and increase in efficiency of the electrolytic cell.

FIG. 1 schematically illustrates an exemplary embodiment of anelectrolytic cell 1 for alkaline water electrolysis with in-situactivation of an anode 10 in accordance with aspects of the presentdisclosure. The anode 10 may be, but not limited to, formed of Nickele.g. as a sheet of Nickel without any surface modification. To explainfurther, the anode 10 is not activated when it is initially positionedin the electrolytic cell 1 and before the electrolysis of the alkalinewater is performed in the electrolytic cell 1 using the anode 10. Theanode 10 is not activated for example, but not limited to, if the anode10 is devoid of any plating or coating on surface of the anode 10 whenit is initially positioned in the electrolytic cell 1 and before theelectrolysis of the alkaline water is performed in the electrolytic cell1.

In some embodiments, the electrolytic cell 1 may be an individual cellor a part of an electrolyser stack (not shown). The other electrode inthe electrolytic cell 1 is a cathode 10. In the cathode 10, at least apart of a surface of the cathode 10 includes an electrically conductingstable material 21 and an anode catalytic material 22. The electrolyticcell 1 also has a diaphragm 30. The anode 10 and the cathode 20 may bepositioned in a container 50 which receives the anode 10, the cathode20, the diaphragm 30, and an electrolyte 40 e.g. alkaline water,provides a seat for performing the alkaline water electrolysis byapplying an external voltage across the anode 10 and the cathode 20 andalso provides a seat for in-situ activation of the anode 10 according toaspects of the present technique. The diaphragm 30 is disposed betweenthe anode 10 and the cathode 20 i.e. the anode 10 and the cathode 20 areseparated by the diaphragm 30. The diaphragm 30 is gas tight.

The diaphragm 30 divides the electrolyte 40 in the container 50 into ananode side 41 of the electrolyte 40 and a cathode side 42 of theelectrolyte 40. The anode side 41 of the electrolyte 40 is the part ofthe electrolyte 40 surrounding the anode 10 whereas the cathode side 42of the electrolyte 40 is the part of the electrolyte 40 surrounding thecathode 20. Oxygen is evolved in the electrolytic cell 1 as a result ofthe OER in the anode side 41 and Hydrogen is evolved in the electrolyticcell 1 as a result of the HER in the cathode side 42. Due to gasimpermeability of the diaphragm 30, the oxygen evolved in the anode side41 is restricted to the anode side 41 and does not pass through theelectrolyte 40 into the cathode side 42, and similarly, the hydrogenevolved in the cathode side 42 is restricted to the cathode side 42 anddoes not pass through the electrolyte 40 into the anode side 41.

FIGS. 2 and 3, respectively, depict exemplary embodiments of theelectrolytic cell 1 in states subsequent to a state depicted in FIG. 1of the electrolytic cell 1. FIG. 4 depicts a flow chart showing anexemplary embodiment of a method 100 for in-situ activation of the anode10 incorporating the present teachings. Hereinafter, the presenttechnique has been explained with help of the electrolytic cell 1 atdifferent subsequent states depicted respectively by FIGS. 1, 2 and 3and by the method outlines by FIG. 4.

Referring to FIG. 1, as depicted therein, at least a part of a surfaceof the cathode 20 includes an electrically conducting stable material22, for example Nickel, and an anode catalytic material 21, for exampleCobalt, Molybdenum, Manganese, Chromium or a combination thereof.Hereinafter, for sake of brevity and ease of understanding, Cobalt hasbeen used as an example for the anode catalytic material 21. The Cobalt21, hereinafter referred to as the Co 21 in the cathode 20 is between 4percentage by mass of the cathode 20 and 30 percentage by mass of thecathode 20, and/or between 10 percentage by mass of the cathode 20 and15 percentage by mass of the cathode 20.

The Co 21 is released from the cathode 20 in the alkaline water 40, i.e.the electrolyte 40, when the electrolyte 40 is present in theelectrolytic cell 1 as depicted in FIG. 2 which shows a part of the Co21 being released from the cathode 20 into the cathode side 42 of theelectrolyte 40. The Co 21 may be released at open circuit potential ofthe electrolytic cell 1 when no external voltage or current is beingapplied to the electrodes 10 and 20 and/or may be released when anexternal voltage is being applied to the electrolytic cell 1, theexternal voltage being applied being the same electrical energy that isapplied to the electrolytic cell 1 for carrying out the electrolysis ofthe electrolyte 40. The electrically conducting stable material 22 isstable in the cathode 20 the electrically conducting stable material 22is not released in the electrolyte or is released in insignificantamount over long period of usage typical of electrolytic cell 1 foralkaline water electrolysis.

The diaphragm 30 is permeable to the Co 21 and allows passage of the Co21, especially in ionic forms for example Cobalt ions with oxidationstates of +2, +3 dissolved in or carried in the electrolyte 40 from thecathode side 42 to the anode side 41 of the electrolyte 40. Suchdiaphragms 30 are commonly used in alkaline water electrolysis and arealso referred to as separator membranes. Since such diaphragms 30 arecommonly used and well known in the art of alkaline water electrolysisthe same has not been detailed here for sake of brevity. The migrationof the Co 21 through the diaphragm 30 and from the cathode side 42 tothe anode side 41 of the electrolyte 40 results from diffusion of theions of the Co 21 and is facilitated by the external voltage applied tothe electrodes 10, 20 of the electrolytic cell 1. The Co 21 when intoelectrolyte 40 at the anode side 41 gets deposited at a surface of theanode 10 under the influence of the electric voltage applied across theanode 10 and the cathode 20. The migration of the Co 21 ions from thecathode side 42 into the anode side 41 of the electrolyte 40 and thesubsequent deposition of the Co 21 ions on the anode 10 is depictedschematically in FIG. 3. The Co 21 ions may get deposited on the anode10 by in form of oxides, hydroxides and oxyhydroxides for exampleCo(OH)3, C03O4.

Also, since the Co 21 leaves the surface of the cathode 20 as depictedin FIGS. 2 and 3, at least a part 24 of the cathode 20 surface becomeporous or gets increased porosity. In the cathode 20 in the electrolyticcell 1, the part of the surface of the cathode 20 may additionallyinclude Sulfur (not shown), the cathode 20 if formed of the electricallyconducting stable material 22 say Nickel, the Co 21 and Sulfur forexample the cathode 20 is Nickel, Cobalt and Sulfur electrode where inthe surface of the cathode 20 has all three—Nickel 22, Cobalt 21 andSulfur.

In some embodiments, the sulfur or parts of the sulfur from the cathode20 during electrolysis in the electrolytic cell 1, also calledelectrolyser, is slowly and continuously removed from the cathode 20into the electrolyte 40 in the electrolyser 1 leaving thereby theelectrically conducting stable material 22 i.e. for example nickel. Thesulfur in the cathode 20 is between 10 percentage and 30 percentage bymass of the cathode 20.

In some embodiments, the release of sulfur from the cathode 20 furtherfacilitates release of the Co 21 from the cathode 20 by either detachingat least some of the Co 21 from the cathode 20 along with the Sulfur'srelease from the cathode 20 and/or modifies the surface of the cathode20 in such a way, for example by creating micro- or nano-sizedprotrusions (not shown) on the surface which are highly unstablemechanically and thus are eventually broken off from the surface of thecathode 20 thereby releasing the Co 21 present in this broken off partsinto the electrolyte 40.

Thus, the sulfur in the cathode 20 facilitates release of the Co fromthe cathode 20 into the electrolyte 40 during alkaline waterelectrolysis. Furthermore, release of sulfur increases the porosity ofthe cathode 20 in the same way as explained in FIGS. 2 and 3 for releaseof the Co 21 and thus results in reduction of the overpotential of thecathode 20 along with the Co 21 induced reduction of the overpotentialof the anode 10. The sulfur may be removed from the electrolyte 40subsequently by filtration and thus maintaining the sulfur contentequilibrium between the cathode 20 and the electrolyte 40 in such a waythat release of sulfur is maintained in a continuous manner whichthereby maintains release of the Co 21 from the cathode 20 in continuousmanner.

In some embodiments, for removal of Sulfur from the electrolyte 40, acomplexing agent may be provided into the electrolyte 40. The complexingagent chemically reacts with the Sulfur present in the electrolyte 40,and also with the Sulfur present in the cathode 20, to form acoordination complex having a solid state. The coordination complex isthen filtered out from the electrolyte 40 and rendering the electrolyte40, and thus the electrolyser 1, at least partially free from the sulfurreleased from the cathode 20. The complexing agent may include, but notlimited to, one or more of Barium hydroxide, Barium chloride, Bariumnitrate, Strontium hydroxide, Strontium chloride, Strontium nitrate,Calcium hydroxide, Calcium chloride, and Calcium nitrate. Generally, theamount of complexing agent when provided to the electrolyte 40 in thecontainer 50 is substantially equal to or less than 1 M (molar)concentration.

The complexing agent reacts with the released sulfur to form thecoordination complex with the released sulfur for example asschematically depicted in the following equation:

SO₄ ²⁻+Ba(OH)₂→BaSO₄+2OH⁻  (i)

Thus, as shown in equation (i) above, the released sulfur for examplethe sulfate ion in equation (i) chemically reacts with the complexingagent for example Barium hydroxide in equation (i) to form coordinationcomplex for example in equation (i) Barium sulfate in solid state i.e.BaS04 (s) in the electrolyte 40 in the container 50. The coordinationcomplex so formed may be removed from the electrolyte 40 by filtration.

Referring now to FIG. 4 in combination with FIGS. 1 to 3, a method 100for activating the anode 10 positioned in the electrolytic cell 1 foralkaline water electrolysis is presented. The method 100 includes a step110 of providing the cathode 20. Subsequently, in the method 100, a step120 of releasing the Co 21 from the cathode 20 is performed.

In the step 120 a part of the Co 21 from the cathode 20 is released fromthe cathode 20 into the electrolyte 40, alkaline water, in theelectrolytic cell 1 by positioning the cathode 20 in the electrolyticcell 1 such the surface of the cathode 20 is contacted with theelectrolyte 40 as shown in FIG. 1. The cathode 20 is positioned suchthat in the electrolytic cell 1 the cathode 20 and the anode 10 areseparated by the diaphragm 30 which also forms the anode side 41 and thecathode side 42 of the electrolyte 40. The step 120 may be performed atopen circuit potential of the electrolytic cell 1 and/or may beperformed when the external voltage is applied to the electrolytic cell1. Finally, in the method 100, a step 140 of depositing the Co 21 isperformed in which at least a part of the co 21 so released is depositedat the anode 10 by applying the electric voltage across the anode 10 andthe cathode 20.

In some embodiments, the method 100 further includes a step 130 ofsustained release of the Co 21 from the cathode 20. The step 130 issubsequent to the step 120, and simultaneous along with the step 140. Inthe step 130 at least a part of the Co 21 from the cathode 20 isreleased from the cathode 20 into the electrolyte 40 along with applyingthe external electric voltage across the anode 10 and the cathode 20.The external electric voltage applied across the electrodes correspondsto a pH of the electrolyte 40 and a molality of the Co 21 present in theelectrolyte 40 as a result of the release from the cathode 20.

FIG. 5 graphically represents a relation between external voltageapplied, pH and release of the Co 21 from the cathode 20. The X axis inthe graph of FIG. 5 represents pH of the electrolyte 40 and the Y axisin the graph of FIG. 5 represents oxidation-reduction potentials forCobalt in Cobalt-water system at 120 degree centigrade and 1.925 barpressure in the electrolyte cell 1. In FIG. 5, reference numeral 80depicts a curve representing Cobalt molality of 1.000E-03 and referencenumeral 90 depicts a curve representing Cobalt molality of 1.000E-09.The graph of FIG. 5 also shows the curves for the OER and the HER. Ascan be seen from the graph of FIG. 5, the Cobalt 21 is not stable aselemental Cobalt 21 in the cathode 20 at external voltages correspondingto current densities of −1.0 V (as shown in Y axis) and pH of 14 to 15(as shown in X axis) for curve 80 and more so for curve 90 as depictedin area of the graph represented by reference numeral 70 in FIG. 5. Whenthe Co 21 is unstable in the cathode 20, the Co 21 is released from theCathode 20 in form of Cobalt oxide ions, Cobalt hydroxide ions, Cobaltoxyhydroxide ions and so and so forth which then migrate within theelectrolyte 40 to the anode 10 and get deposited at the anode 10 in formof Cobalt (11, 111) oxide (C03O4), Cobalt (III) hydroxide, and so on andso forth.

As a result of deposition of the Cobalt 21 at the anode 10, theoverpotential at the anode 10 is decreased. The following table providespotential of the electrolytic cell 1, the anode 10 and the cathode 20under different conditions:

Anode Cathode Cell potential potential potential vs Hg/HgO vs Hg/HgOAnode Cathode (mV) (mV) (mV) Ni Ni 2101 657 −1467 Externally Ni 1982 553−1454 Activated Ni Ni Externally 1664 506 −1154 activated Activatedin-situ Ni according to the present technique Externally Externally 1649510 −1135 Activated Activated Ni Ni

The anode and cathode potentials are expressed in comparison to aMercury/Mercury Oxide reference electrode. The values in the table aremeasured at 100 degree Centigrade, 50 wt % KOH as the electrolyte 40,external current at 0.2 A/cm square of each of the electrode, Zero-gapconfiguration, and total electrode area for each electrode as 25 cmsquare.

As can be seen in the table above, in first row both the anode 10 andthe cathode 20 are not activated for example when sheets of Nickel areused as the cathode and the anode without any coating for activation orsurface modification for activation, and the cell potential is 2101 mV(millivolts) which is contributed primarily by the anode potential of657 mV and cathode potential of −1467 mV. Second row of the table onlythe anode 10 is activated externally ex-situ, contrary to our technique,and the cathode 20 is not activated and the cell potential is 1982 mVwhich is contributed primarily by the anode potential of 553 mV andcathode potential of −1454 mV. The fourth row presents a scenario whereboth the anode 10 and the cathode 20 are activated externally ex-situ,the cell potential is 1649 mV which is contributed primarily by theanode potential of 510 mV and cathode potential of −1135 mV. The thirdrow represent the scenario arising from the present technique, i.e. thecathode 20 is activated and includes the anode catalytic material 21which then is released into the electrolyte 40, migrated to the anode 10and is deposited on the anode 10, and as can be seen from the third row,the cell potential is 1664 mV which is contributed primarily by theanode potential of 506 mV and cathode potential of −1154 mV—thus thecell potential for the present technique is substantially similar to thecell potential of fourth row, where both the anode and the cathode wereex-site activated separately.

While the present technique has been described in detail with referenceto certain embodiments, it should be appreciated that the presenttechnique is not limited to those precise embodiments.

Rather, in view of the present disclosure which describes exemplarymodes for practicing the invention, many modifications and variationswould present themselves, to those skilled in the art without departingfrom the scope and spirit of this invention. The scope of the inventionis, therefore, indicated by the following claims rather than by theforegoing description. All changes, modifications, and variations comingwithin the meaning and range of equivalency of the claims are to beconsidered within their scope.

What is claimed is:
 1. An electrolytic cell for alkaline waterelectrolysis with in-situ anode activation, the electrolytic cellcomprising: an anode; a cathode wherein at least a part of a surface ofthe cathode comprises an electrically conducting stable material and ananode catalytic material adapted to be released from the surface of thecathode in alkaline water and be deposited at a surface of the anodewhen an electric voltage is applied across the anode and the cathode;and a diaphragm separating the anode and the cathode, wherein thediaphragm is gas tight and is permeable to the anode catalytic material.2. The electrolytic cell according to claim 1, wherein the electricallyconducting stable material comprises Nickel.
 3. The electrolytic cellaccording to claim 1, wherein the anode catalytic material comprises atleast one of Cobalt, Manganese, Molybdenum, Chromium, and a combinationthereof.
 4. The electrolytic cell according to claim 1, wherein theanode catalytic material comprises between 4 percentage and 30percentage by mass of the cathode.
 5. The electrolytic cell according toclaim 1, wherein the at least part of the surface of the cathode furthercomprises Sulfur.
 6. The electrolytic cell according to claim 1, whereinthe anode consists of Nickel.
 7. A method for in-situ anode activationof an anode positioned in an electrolytic cell for alkaline waterelectrolysis, the method comprising: providing a cathode wherein atleast a part of a surface of the cathode comprises an electricallyconducting stable material and an anode catalytic material, the anodecatalytic material adapted to be released from the cathode in alkalinewater; releasing anode catalytic material from the cathode into anelectrolyte in the electrolytic cell by positioning the cathode in theelectrolytic cell such the at least a part of the surface of the cathodeis in contact with the electrolyte; wherein the electrolyte comprisesalkaline water; the cathode is separated from the anode in theelectrolytic cell by a gas tight diaphragm permeable to the anodecatalytic material; and depositing at least a part of the anodecatalytic material so released surface of the anode by applying anelectric voltage across the anode and the cathode to reduce anoverpotential at the anode.
 8. The method according to claim 7, whereinreleasing the anode catalytic material from the cathode into theelectrolyte takes place at an open circuit potential of the electrolyticcell.
 9. The method according to claim 7, further comprising anadditional release of the anode catalytic material from the cathode atleast a part of the anode catalytic material is released from thecathode into the electrolyte while applying the external electricvoltage across the anode and the cathode.
 10. The method according toclaim 9, wherein the external electric voltage applied across the acrossthe anode and the cathode corresponds to a pH of the electrolyte and amolality of the anode catalytic material present in the electrolyte. 11.The method according to claim 7, wherein the electrically conductingstable material comprises Nickel.
 12. The method according to claim 7,wherein the anode catalytic material comprises at least one of Cobalt,Manganese, Molybdenum, Chromium, and a combination thereof.
 13. Themethod according to claim 12, wherein the anode catalytic material inthe cathode comprises between 4 percentage and 30 percentage by mass ofthe cathode.
 14. The method according to claim 7, wherein the at least apart of the surface of the cathode further comprises Sulfur.
 15. Themethod according to claim 7, wherein the anode consists of Nickel. 16.The electrolytic cell according to claim 1, wherein the anode catalyticmaterial comprises between 10 percentage and 15 percentage by mass ofthe cathode.
 17. The method according to claim 12, wherein the anodecatalytic material in the cathode comprises between 10 percentage and 15percentage by mass of the cathode.